The investigations have as their goals: 1) To determine whether neurite outgrowth capabilities of statoacoustic ganglion neurons occurs for only a limited period or is present for an extended period during embryonic development of the inner ear; 2) To define the onset and duration of attractant fields produced by embyronic otic sensory receptors; 3) To examine the specificity of the otic sensory epithelium attractant fields for stimulating directed neuritic outgrowth from neurons of various ganglia; 4) To test the specificity of statoacoustic ganglion directed neuritic outgrowth in response to various embryonic tissues as targets. A series of three experiments will utilize the techniques of organ culture, embryonic microsurgery with tissue recombinations, special histology, ultrastructure and time-lapse cinematography. These experiments are designed to further our understanding of the cellular nature of statoacoustic ganglion-otic sensory receptor interaction during development of the inner ear. The information gained should test and act to further refine the hypothesis that a mechanism for guiding neuritic elements of statoacoustic ganglion neurons to their appropriate target tissues within the inner ear is the establishment of attracting fields by differentiating otic sensory epithelia to which nerve growth cones of ingrowing afferent neurites are attracted. These studies may also advance our basic understanding of the development of a sensory neural system and, in particular, the factors which are operant in the orderly and appropriate connecting of a neuron and a sensory receptor cell. There is a need for knowledge of how sensory receptor - neuron connections are made in the inner ear so that these findings can be possibly applied to understanding specific disorders of the inner ear.